Question

Решите пожалуйста очень нужно

Answer 1

$\displaystyle\bf\\7x^{2} +x-1=0\\\\Teorema \ Vieta \ :\\\\x_{1} + x_{2} =-\frac{1}{7} \\\\\\x_{1} \cdot x_{2} =-\frac{1}{7} \\\\\\\frac{1}{x_{1} ^{2} } +\frac{1}{x_{2} ^{2} } =\frac{x_{1} ^{2} +x_{2} ^{2} }{(x_{1} \cdot x_{2} )^{2} } = \frac{(x_{1} +x_{2} )^{2} -2x_{1} \cdot x_{2} }{(x_{1} \cdot x_{2} )^{2} } =$

$\displaystyle\bf\\=\frac{\Big(-\dfrac{1}{7} \Big)^{2}-2\cdot\Big(-\dfrac{1}{7}\Big) }{\Big(-\dfrac{1}{7}\Big)^{2} } =\frac{\dfrac{1}{49} +\dfrac{2}{7} }{\dfrac{1}{49} } =\frac{15}{49} \cdot 49=15$